First I'm just going to give a bit of backround info on me, I started officiating basketball and then moved into football. So I had two years of experience with basketball rules and mechanics before I threw my first flag (and this happened to be it)
This is a tyke(age 7-9) game and I'm the LJ. The QB breaks out on this running play goes about 20 yards downfield. I see one of his teammates holding a defensive player right behind him, I instictively blow my whistle and "bird dog". Then I realized I was on the football field and tossed my flag up.
Needless to say, I was told to switch to a finger whistle before my next games. (something I still haven't done 2 years later
)